Washington: US Defense Secretary Robert Gates says that ‘somebody’ in Pakistan knew about slain al-Qaeda leader Osama bin Laden's hideout in that country but there is no ‘evidence’ that the top leadership was aware of it.

Gates would not say who knew about the presence of Laden in Abbottabad deep inside Pakistan but suggested it could have been retired or low-level Pakistani officials.

At a Pentagon news conference, Gates also said Pakistan already has paid dearly for its failure to acknowledge the fact that Laden was hiding for more than five years in a compound a short distance from a Pakistani military facility. Admiral Mike Mullen, Chairman of the Joint Chiefs of Staff, echoed similar sentiments.

"I have seen no evidence at all that the senior leadership knew. In fact, I have seen some evidence to the contrary. But we have no evidence yet with respect to anybody else. My supposition is: Somebody knew," Gates said at a Pentagon news conference.

At the same news conference, Mullen endorsed Gates' assessment and said, "I have seen no evidence that the top leadership knows.about it"

"With the evaluation of the sensitive site material and exploitation that's going on, it's just going to take us a while to see if there's anything else," Mullen said.

Gates also said the US has humiliated Pakistan by carrying out with impunity its covert operation in Abbottabad that killed the 9/11 mastermind.

"If I were in Pakistani shoes, I would say I've already paid a price (for terrorist safe havens). I've been humiliated. I've been shown that the Americans can come in here and do this with impunity. I think we have to recognize that they see a cost in that and a price that has been paid," he said.

Mullen also said that one should not underestimate the humiliating experience of Pakistan after the bin Laden operation.

"I don't think we should underestimate the humbling experience that this is. In fact, the internal soul-searching that's going on inside the Pak military right now and the impact of that, before you even start to talk about external effects," Mullen said.

Mullen has been in constant contact with the Pakistani leadership in particular with its Army Chief General Ashfaq Pervez Kayani. In the past two years, he has travelled to Pakistan at least two dozen times.

Mullen said the US needs to give Pakistan some time and space to work on some of the internal challenges that came out of this, while at the same time the things that there are some near-term things that we think actions need to be taken.